Communications over electric power lines has the advantage over other forms of communication since most residential and commercial structures are wired with electric conductors carrying line current to the structure. Since these structures are already "wired", this affords an excellent opportunity to take advantage of existing infrastructure for communication systems.
Various forms of communication over power lines are known in the art. For example, U.S. Pat. No. 4,885,563 to Johnson et al., issued Dec. 5, 1989 entitled "POWER LINE CARRIER COMMUNICATION SYSTEMS" describes a power line carrier system uses a current carrier transceiver as the communications interface to the power line. This system using FSK modulation over the power line but suffers in a noisy environment and is prone to noise corruption of data. Other patents related to Johnson et al. are U.S. Pat. No. 4,885,564 and U.S. Pat. No. 4,896,277.
U.S. Pat. No. 3,942,168 to Whyte issued Mar. 2, 1976 entitled "DISTRIBUTION NETWORK POWER LINE COMMUNICATION SYSTEM" describes a pulse with a modulated FSK signal impressed upon a power line at approximately 100 to 102 kilohertz. The signal has a fixed mark-space protocol such that the timing of the ONE (mark) and the ZERO (space) frequencies of the FSK signal are always the same. This system, like Johnson et al., suffers from noise corruption of data signals in a noisy power line environment.
There is a need in the art for a power line communication system for transmitting and receiving digital information which is noise immune and which detects when information is truly corrupted by noise.